A coach wants to know if baseball players who warm up before a game will score more points than those who don't warm up. He will break the team up into two groups and make sure each player gets equal time on the field. He will then count how many points each player makes during the game. What statistic should he study?

The mean number of points earned by each player
The standard deviation of the number of points earned by each player
The standard deviation of the number of points earned by each group
The mean number of points earned by each group